1. Field of the Invention
The present invention relates to a device for coupling two electromagnetic contactors to each other in a reversible electromagnetic contactor insertable in a reversible control circuit of an electric motor or the like and arranged to operate so that only one of the electromagnetic contactors is turned on even when an input signal is simultaneously applied to both of the electromagnetic contactors.
2. Related Art
FIG. 1 shows an example of a conventional reversible electromagnetic contactor provided with a mechanical interlock unit that prevents two electromagnetic contactors from turning on at the same time even if an input signal is simultaneously applied to the two electromagnetic contactors. In FIG. 1, reference numerals 1 and 2 designate electromagnetic contactors. The electromagnetic contactors 1 and 2 are integrally coupled to each other by means of a coupler 4 with a mechanical interlock unit 3 interposed between the contactors 1 and 2. The mechanical interlock unit 3 is arranged to prevent the two electromagnetic contactors 1 and 2 from turning on at the same time even when an input signal is simultaneously applied to the two electromagnetic contactors 1 and 2. Such a mechanical interlock unit has been well known as shown by Japanese Utility Model Post-Examination Publication No. 11311 (entitled "Mechanical Locking Device for Electromagnetic Contactors").
FIG. 2 is a perspective view showing a lower half portion of the reversible electromognetic contactor of FIG. 1 viewed from the bottom side thereof. In FIG. 2, the electromagnetic contactors 1 and 2 are attached so as to be mounted on a U-shaped support rail (not shown). Rail hanging portions 1a and 2a, and sliders 1b and 2b are provided on the bottoms of the electromagnetic contactors 1 and 2 respectively. The sliders 1b and 2b have been well known as shown, for example, by Japanese Utility Model Post-Examination Publication No. 54-10455 (entitled "Device for Attaching Electric Appliance onto Rail"), and are made slidable vertically in the drawing.
The electromagnetic contactors 1 and 2 are attached to the support rail in such a manner that the rail hanging portions 1a and 2a are hung at one end of the U-shaped support rail, and then the sliders 1b and 2b are pressed against the other end of the support rail so that the sliders 1b and 2b move downward in the drawing. If the respective top ends of the sliders 1b and 2b have gotten over the support rail, the sliders 1b and 2b return to the positions shown in the drawing so that the support rail is grasped between the rail hanging portions 1a and 2a and the sliders 1b and 2b. The support rail is adapted to be attached to recess portions 1c and 2c.
Two engagement grooves 1f are formed in each of the opposite side surfaces of the electromagnetic contactor 1 and two engagement grooves 2f are formed in each of the opposite side surfaces of the electromagnetic contactor 2. A coupler 4 (FIG. 3) having two engagement portions 4a formed on each of its opposite side surfaces corresponding to the engagement grooves 1f and 2f is inserted between the electromagnetic contactors 1 and 2 to couple the electromagnetic contactors 1 and 2 to each other. Because the interlock unit 3 is sandwiched between the electromagnetic contactors 1 and 2, the coupler 4 is inserted from the bottom side of the electromagnetic contactors 1 and 2.
However, the coupling described above has problems because no particular force for sandwiching the interlock unit 3 is exerted between the electromagnetic contactors 1 and 2. Therefore, the engagement portions of the interlock unit 3 with the electromagnetic contactor 1 and 2 may be abraded owing to vibrations during operation of the electromagnetic contactors, or when the electromagnetic contactors 1 and 2 are simultaneously turned on, a force may be exerted on the interlock unit 3 so that the electromagnetic contactors 1 and 2 escape outward as shown by an arrow in FIG. 1 to change the relative position between the intelock unit 3 and the electromagnetic contactors 1 and 2, and lower the interlocking function.
Further, in the case where the two electromagnetic contactors 1 and 2 are different in height from each other, if the coupler 4 is pressed into place between the electromagnetic contactors 1 and 2 while the upper surfaces of the respective electromagnetic contactors 1 and 2 are fixed so as to agree with a work surface 15 as shown in FIG. 4, a step difference is produced between the electromagnetic contactors 1 and 2 as shown in the drawings so that the positions of the rail fitting recess portions 1c and 2c are uneven with respect to each other.
The problem of such a step difference may be solved by partially inserting the coupler 4 between the electromagnetic contactors 1 and 2 so as to be fixed therebetween provisionally when the electromagnetic contactors 1 and 2 are in a laid down condition. The electromagnetic contactors 1 and 2 are then raised so as to make the coupler 4 abut on the work surface 15 as shown in FIG. 5. Then the electromagnetic contactors 1 and 2 are pressed down so that the bottom surface 1d and 2d of the respective electromagnetic contactors 1 and 2 abut on the work surface 15. Thus, the rail-fitting recess portions 1c and 2c of the respective electromagnetic contactors 1 and 2 become even with each other as shown in FIG. 6. In this condition, however, the rail fitting recess portions 1c and 2c are closed or blocked by the coupler 4. To solve this blockage problem, the coupler 4 may be pushed into place between the electromagnetic contactors 1 and 2. However, if the electromagnetic contactors 1 and 2 are turned upside down in order to insert the coupler 4, the problem as shown in FIG. 4 occurs because the electromagnetic contactors 1 and 2 differ in height from each other.